Fluid-operated cylinder

ABSTRACT

A fluid-operated cylinder in which sealing between the piston and the cylindrical housing is provided by a tubular element of resilient material, such as rubber, plastics material and the like which is placed in said cylindrical housing and extends to a length at least equal to the piston stroke.

United States Patent Panigati [54] FLUID-OPERATED CYLINDER [72] Inventor: Pier Luigi Panigati, Via Friuli 72,

Milan, Italy 221 Filed: Dec. 29, 1969 211 Appl.No.: 4,181 I [30] Foreign Application Priority Data [4 1 Oct. 10, 1972 Primary Examiner-Martin P. Schwadron Assistant Examiner-Allen M. Ostrager Att0rney-Guido Modiano and Albert Josif NOV. 1 l, 1969 Italy ..24269 A/69 I 57 ABSTRACT A fluid-operated cylinder in which sealing between the 8| piston and the cylindrical housing is provided y a m n 92 170 bular element of resilient maeri all, such as rubber, Fled of Search .7" l material and the which is placed in said cylindrical housing and extends to a length at least References Cited equal to the piston stroke.

UNITED STATES PATENTS 3,084,717 4/1963 Purcell ..92/170 x 858 3/1927 7 h wqp '"f?'f117tf'f"f92 1 O. t 7a 5a 8 l/ I PATENTEDnm 10 1912 SHEET 1 OF 2 INVENTOR. IER LUIGI PANIGATI AGENT PATENTEDHBI 1m 3,696,714 sum 2 0F 2 INVENTOR.

PIER LUlGl PANIGATI AGENT FLUID-OPERATED CYLINDER BACKGROUND OF THE INVENTION The present invention relates to a fluid-operated cylinder both for single and double acting uses.

As is known, the sealing between the piston and the cylindrical wall in fluid-operated cylinders is obtained by seals or gaskets of resilient material provided on the lateral surface of the piston.

Such seals, however, undergo a remarkable wear due to the continuous reciprocating movement of the piston, thus quite frequent replacement of these seals is required.

The main object of the present invention is that of providing a fluid-operated cylinder where the sealing between piston and housing is obtained for a much longer time period than that permissible in the cylinders in use at present.

Another object is that of providing a fluid-operated cylinder which can be manufactured at a lower cost than the known types, the performance being equal.

Another object of thisinvention is that of providing a fluid-operated cylinder of rational design and of efficient and regular operation.

SUMMARY OF THE INVENTION These and still further objects are attained by a fluidoperated cylinder according to the invention, characterized in that the sealing between piston and cylindrical housing is obtained by means of a tubular element of resilient material, such as rubber, plastics material or the like, which extends to a length at least equal to the piston stroke length and is arranged in such manner as to define the said cylindrical housing in which the said piston is slidably mounted, the latter being peripherally rounded and having a maximum diameter slightly greater than the inner diameter of the said tubular element.

BRIEF DESCRIPTION OF THE DRAWINGS Further characteristic features and advantages of the invention will better appear from the detailed description of a preferred, not exclusive, embodiment of a fluid-operated cylinder according to the invention, which is illustrated by way of not-limiting example in the following drawings, in which:

FIG. 1 is an axial section view of the fluid-operated cylinder according to the invention;

FIGS. 2, 3 and 4 are partial axial section views of three respective embodiments of the fluid-operated cylinder according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1 the fluid-operated cylinder according to the invention consists of a tubular metal housing 1, preferably cylindrical in shape, within which a tubular element or liner is arranged which is also preferably of cylindrical shape and consisting of resilient material, such as rubber, plastics material or like elastomeric material. The tubular element 2 defines a cylindrical space or chamber and extends to a length slightly longer than that of the piston stroke.

According to a known arrangement the fluidoperated cylinder includes heads 3 which may be provided both for single and double-acting operation.

Fixed to the stem 4 of the cylinder is a piston 5 without gaskets or seals and having a maximum diameter slightly larger than the inner diameter of the tubular element 2. With this arrangement the piston 5 causes the tubular element 2 to deform by pressing the same so as to provide the sealing. From FIG. 3 it appears clear that the liner 2c is pressed against the housing 1 thereby separating the interspace between the liner 2c and the housing 1 in two portions. The piston 5 secured to the stem 4, such as by welding, also has a rounded outline in order to permit the sliding movement within the cylindrical space without damaging the tubular element 2, thus also reducing friction along the contact surface.

As is lecally shown in FIG. 1, the rim 5a of the piston 5 has an arcuated outline in cross-section, which approximates a semicircle.

A turn out edge 2a at each end of the tubular element 2 is provided which is arranged to secure the tubular element 2 to the heads 3 and to engage with a respective metal ring 6 which is positioned between the tubular housing 1 and the said tum-out edge 2a. A ring 7 is also connected to each end of the cylindrical housing 1, which has an inner shoulder 7a against which a ring 8 fixed to the cylindrical housing 1, abuts this ring 8 may consist, for example, of an elastic steel ring). The ring 7 is connected to the relative head 3 by means of screws 9 which are screwed into relative threaded holes formed in the ring 7. By this arrangement at each end of the cylinder the ring 7 and head 3 may approach one another when screws 9 are tightened, thus causing the tum-out edge 2a to be pressed by the metal ring 6. By screwing the screws 9, the ring 7 acts on the ring 8 which is fixed to the cylindrical housing 1 and thus causes the latter to urge against the metal ring 6 and to press the tum-out edge 2a of the tubular element 2. Obviously this is a relative movement in so far as the cylindrical housing 1 being considered stationary, the screwing of the screws 9 causes the heads 3 to move towards the cylindrical housing.

From the above the operation of the fluid-operated cylinder according to the invention should appear evident.

During the reciprocating movement of the piston 5 within the cylindrical space, the rim 5a of this piston presses and slightly stresses the tubular element 2, because as stated above, the maximum diameter of piston 5 is greater than that of the inner diameter of the tubular elements 2, thus providing an effective sealing. The reciprocating movement of the piston 5 will cause wearing on the whole inner surface of the tubular element 2 between the heads 3. This is advantageous when bearing in mind that in conventional cylinders wear occurs on the gasket which is carried by the piston and is friction stressed during the whole piston stroke.

In other words in the fluid-operated cylinder according to the invention, the work point continuously moves along the tubular element 2, thus the wear is distributed on a large surface and a longer useful life is attained. It is thus possible to provide a sealing life considerably longer than that possible with conventional cylinders.

According to the embodiments shown in FIGS. 2, 3 and 4, the arrangement is completely similar to that described above except that the tubular element of resilient material is so arranged as to define a gap or tubular interspace with the cylindrical housing 1.

This interspace contains an interspace fluid which is the same as the cylinder operating fluid.

In these embodiments the tubular element of resilient material has a thickness lower than that of the tubular element 2 in FIG. 1.

Also the securing system of the tubular element of resilient material in such embodiments is substantially the same as that described above. The only difference is shown by the metal ring 60 which has an L-shaped cross-section instead of the rectangular cross-section of the metal ring 6 in FIG. 1.

The said L-shaped cross-section of the metal ring 6a defines in fact the gap between the tubular element of resilient material and the cylindrical housing 1.

While in the embodiment of FIG. 2 a continuous tubular element 2b of resilient material is provided, tubular elements 20 and 2d, respectively, are provided with holes at the ends thereof in the embodiments shown in FIGS. 3 and 4.

More precisely the tubular element 20 in FIG. 3 is formed with simple holes 10 at the ends thereof, while the tubular element 2d in FIG. 4 is provided with holes 1 1 having tabs 11a outwardly which act as single direction valves.

The operation in the embodiments shown in FIGS. 3, 4 and 5 is completely similar to that described above, one difference being that the tubular elements of resilient material are deformed to a larger extent, as clearly shown in the same Figures.

In the embodiment in FIG. 2 the pressure in the gap between the tubular element 212 and the cylindrical housing 1 is not controlled since this gap is tight-sealed.

In the embodiment in FIG. 3 the holes communicate the gap between the tubular element 2c and the cylindrical housing 1 with the relative work spaces defined by the piston 5. A fluid flow thus occurs throughout said holes 10.

In the embodiment in FIG. 4 such fluid passage is controlled by the single direction valves defined by the holes 11 and the relative tabs 11a.

The fluid can thus enter the gap through the holes 1 l, but cannot come out.

The presence of the fluid in the gap between the tubular elements of resilient material and the cylindrical housing 1, in the embodiments shown in FIGS. 3, 4 and 5 causes the tubular elements to keep suitably against the rim of the piston 5. The tubular elements of resilient material in all the above-mentioned embodiments are mounted with a slight tensioning lengthwise.

It should be appreciated that the fluid-operated cylinder according to the invention provides a regular and safe operation with a long useful life of the sealing between piston and cylindrical housing. Accuracy requirements in the geometrical and physical characteristics of the tube are also reduced, and thus the fluidoperated cylinder according to the invention may be manufactured at a lower cost relatively to the known types by making use of less costly material which may be machined with relatively large tolerances.

The structure according to the invention also permits a ready manufacturing of cylinders having a standart section and of any shape (square or another form) so that the overall dimensions of the parallepipedon being equal, the trust surface is greater and rotation is prevented at the same time.

Fu ermore the structure according to the invention pennits long stroke cylinder being readily manufactured.

Finally the cylinder according to the invention may be manufactured for particular applications only with the tubular element of resilient material, thus dispensing with the holding outer housing 1.

The invention thus conceived is susceptible to numerous modifications and changes all of which are included in the scope of the invention. The used materials as well as dimensions can be any according to the requirements and all elements can also be substituted by other technically equivalent means.

Iclaim:

1. A fluid operated cylinder including a cylindrical housing, a piston slidable therein and a sealing member between said piston and said cylindrical housing, said sealing member being in the fonn of a deformable liner of substantially elastomeric material, said liner defining a cylinder cavity and extending over a length at least equal to the piston stroke length and allowing slidable movement of the piston therein, the normal diameter of said deformable liner being normally less than the inner diameter of said cylindrical housing thereby forming a tubular interspace therebetween, an interspace fluid within said interspace and wherein, according to the improvement, said liner has at least one opening at least near the end of stroke position of the piston, said opening providing communication between said tubular interspace and said cylinder cavity, said interspace fluid being the same as the cylinder operating fluid contained within said cylinder cavity and said piston having a diameter greater than the normal diameter of said liner and such as to press the liner portion nearest to said piston against the cylinder walls so as to separate thereby said interspace in two portions. 

1. A fluid operated cylinder including a cylindrical housing, a piston slidable therein and a sealing member between said piston and said cylindrical housing, said sealing member being in the form of a deformable liner of substantially elastomeric material, said liner defining a cylinder cavity and extending over a length at least equal to the piston stroke length and allowing slidable movement of the piston therein, the normal diameter of said deformable liner being normally less than the inner diameter of said cylindrical housing thereby forming a tubular interspace therebetween, an interspace fluid within said interspace and wherein, according to the improvement, said liner has at least one opening at least near the end of stroke position of the piston, said opening providing communication between said tubular interspace and sAid cylinder cavity, said interspace fluid being the same as the cylinder operating fluid contained within said cylinder cavity and said piston having a diameter greater than the normal diameter of said liner and such as to press the liner portion nearest to said piston against the cylinder walls so as to separate thereby said interspace in two portions. 